The invention relates generally to an ultrasonic transducer and more specifically concerns an ultrasonic transducer with a Gaussian radial pressure distribution.
In materials evaluation applications requiring the interrogation of the modified far field pattern of an ultrasonic transducer it is desirable to use the transducer which produces a beam with a Gaussian profile. A simplified theoretical analysis of several bulk ultrasonic phenomenon require the consideration of bounded ultrasonic beams having velocity distributions which are Gaussian as a function of radius. Additionally, since the beam profiles in the near field and far field regions are related by a Fourier transform operation, Gaussian profile beams are particularly useful in experimental situations in which a similarity between a near and far field pattern is desired.
A standard prior art surface contact transducer typically generates a field which is approximately uniform in the region near its contact surface (FIG. 1a) and negligible elsewhere. The resulting far field pattern thus contains significant sidelobe maxima, as shown in FIG. 1b, which may be difficult to distinguish from the central beam in experiments involving beam translation and attenuation. Several transducer designs employing single electrodes of various shapes have been designed to provide a field which when averaged around the radii is a Gaussian function of radius. These electrode designs, however, introduce a distribution that is a function of angular displacement on the face of the transducer and not purely a function of radius. In the Journal of the Acoustical Society of America, vol. 49, pp 1668-1669, a method is described for generating a velocity distribution which is Gaussian utilizing multiple linear electrodes. However, this Gaussian function is in one dimension only.
An object of this invention is to provide an ultrasonic transducer that produces an output having a Gaussian profile.
Another object of this invention is to provide an ultrasonic transducer that produces an output having a Gaussian profile as a function of radius.
A further object of this invention is to provide an ultrasonic transducer that produces an output in which all cross-sections of the output through the center of the output is a Gaussian function.
Still another object of this invention is to provide an ultrasonic transducer that produces an output having a Gaussian profile and in which a far field pattern of the output is similar to a near field pattern of the output.
A still further object of this invention is to provide an ultrasonic transducer that produces an output that is a symmetrical function. Symmetrical function as used in this specification means a function such that the second half of the function if it were folded back on the first half of the function would coincide with the first half of the function. In other words, for every point on the first half of the function there is a corresponding, equal amplitude, equal distance from the center of the function, point on the second half of the function.
Yet another object of this invention is to provide an ultrasonic transducer that produces an output such that any cross-section of the output through its center is a symmetrical function.
Other objects and advantages of this invention will become apparent hereinafter in the specification and drawings.